German da- and wo- words — darauf, damit, worauf, womit

English says I am waiting for it and what are you waiting for? German cannot do either. A preposition in German never takes es as its object, and it never gets stranded at the end of a question. Instead the preposition fuses with da- or wo- and becomes one word.

Ich warte darauf. — I am waiting for it.

Worauf wartest du? — What are you waiting for?

This is one of the most German things in the language, and there is nothing in English to map it onto — which is why it stays unfamiliar long after the grammar behind it is understood.

The rule

da- + preposition replaces it, them, that. wo- + preposition asks what ...?

If the preposition begins with a vowel, an r goes in to make it sayable: da-r-auf, wo-r-an.

Only for things, never for people

This is the limit of the rule, and it is absolute. If the object is a person, the preposition stays separate and takes an ordinary pronoun.

Ich denke daran. — I am thinking about it.

Ich denke an sie. — I am thinking about her.

Same verb, same preposition, and the only thing that decides the form is whether the object breathes.

Where you meet it: verbs with a fixed preposition

The reason this comes up constantly is that a large number of German verbs are welded to a preposition, and the moment you want to say "about it" or "for it", you need the da- form.

The verb-plus-preposition pairs are vocabulary rather than grammar: the German preposition rarely matches the English one, and each has to be learned attached to its verb. There is more on the reflexive ones in German reflexive verbs.

Pointing forward to a clause

The da- form also announces a clause that has not arrived yet. It stands in for the whole thing that follows.

Ich freue mich darauf, dich zu sehen. — I am looking forward to seeing you.

Ich warte darauf, dass er kommt. — I am waiting for him to come.

The darauf is not optional. German needs it there to hold the preposition's place, and leaving it out is one of the mistakes that marks a sentence as foreign even when every word is right.

damit has two jobs

damit is both with it and the conjunction so that. The two are told apart by what follows, and by the stress in speech.

Ich schreibe damit. — I write with it. (da-mit, stress on da)

Ich lerne, damit ich die Prüfung bestehe. — I study so that I pass the exam. (conjunction, verb to the end)

The second sends its verb to the end, which is the giveaway — see German subordinate clauses.

What to actually memorise

The rule itself is one line: things get da- and wo-, people keep the preposition and a pronoun. What takes time is the verb-plus-preposition list, and that is vocabulary you pick up a pair at a time.